Temperatures are rising across central and eastern Australia as days of searing heat move in.

Oodnadatta, in northern South Australia, had reached 37.5 degrees by 9.30am (local time) on Friday.

It is forecast to reach 44, with 47 degrees to follow on Saturday.

In NSW, Dubbo had hit 28 degrees by about the same time – with a forecast top of 40 on Friday, followed by another on Saturday.

The major cities won’t escape the heat either. Adelaide is forecast to hit 40 on Friday and 38 on Saturday.

Sydney is forecast to hit 39 degrees on Sunday, while some records are expected to be broken in western NSW. Parts of Sydney’s west are likely to hit the low 40s for several days.

Melbourne will reach the mid-30s on Friday, but a southerly change late in the day means will be spared the worst of the high temperatures. That won’t apply to northern Victoria, which is also expecting to be in the low 40s for several days.

Tweet from @BOM_NSW

NSW Health issued a heatwave alert on Friday.

“We are urging people to avoid being outside during the hottest part of the day, to keep well hydrated, and to look after vulnerable neighbours and relatives,” acting director of environmental health Dr Adi Vyas said.

“Hot weather puts a lot of strain on the body, causes dehydration and can make underlying health conditions worse. It also causes heat stress and heat stroke. People over 75, people with chronic medical conditions and people who live alone are particularly vulnerable.”

He said NSW residents should keep in touch with isolated neighbours, family and friends – but also be mindful of COVID safety.

The heatwave will also bring a very high to severe fire risk. The heat will last into Monday, when it will move north into southern Queensland.

NSW Rural Fire Service Deputy Commissioner Peter McKechnie has urged people to have a fire plan ready and prepare their properties.

“This is the first time since the devastating season last year we’ve seen widespread elevated fire danger,” he said on Friday.

“Know what to do if a fire threatens you, know where you’ll go.”

NSW’s south-west will experience the worst of the fire conditions on Saturday, before the scorching weather moves through Sydney, the Hunter Region and north coast on Sunday.

Mr McKechnie said grassland areas west of the Blue Mountain ranges were of particular concern, as were the windy conditions.

“These are dangerous conditions, fires will start easily and they’ll spread very quickly,” he said.

Last summer’s bushfires destroyed 2476 homes, claimed 26 lives and burned 5.5 million hectares of land.

Tweet from @BOM_SA

The BOM Head of Operational Climate Services Dr Andrew Watkins said “even short periods of hot and dry weather increase the risk of fire in summer’.

“This summer heatwaves may not reach the extreme temperatures of recent years, but may be of longer duration and more humid, which can still have a significant impact on human health,” he said on Thursday.

Tweet from @WaverleyCouncil

The BOM noted the weekend would bring temperatures up to 10 to 16 degrees above the average across the state for this time of the year.

“NSW will not be spared with temperatures climbing easily into the mid 40s for vast swathes of the western part of the state and even into the low 40s for some coastal areas,” meteorologist Helen Reid said.

“It will also be quite windy so we are keeping a close eye on the fire danger which is associated with this warm, heatwave situation,” Ms Reid said.

“It is going to be quite a volatile situation.”

A cooler gusty change is tipped to cross the state on Sunday and into Monday, but temperatures are expected to rise again on Tuesday.

The cool front was likely to pick up dust that could reach Canberra, the BOM said.

-with AAP